Outcomes after lung transplantation remain significantly worse than after transplantation of other organs. Ischemia reperfusion injury is the leading cause for early morbidity and mortality after lung transplantation and has also been shown to be a risk factor for chronic lung rejection demonstrating its long-term effect on allografts. However, the role of ischemia reperfusion injury in regulating lung allograft rejection is not clear largely due to a lack of physiological mouse model of lung transplantation. New data from our laboratory has shown that prolonging cold ischemia from 1 hour to 18 hours induces the acute rejection of mouse lung allografts in recipients treated with perioperative blockade of CD154-CD40 and CD28-B7 pathways. This acute rejection is associated with an altered balance of regulatory and effector T cells in the allografts. The aim of this proposal is to perform mechanistic studies in the orthotopic mouse lung transplant model to investigate how ischemia reperfusion injury-associated signals regulate adaptive immune responses that lead to allograft rejection. The first aim of this grant will examine how Toll-like receptor signaling regulates lung allograft rejection after prolonged ischemia. The second aim will evaluate how downstream inflammatory signals associated with ischemia reperfusion injury regulate the balance between effector and regulatory T cells after lung transplantation and control lung allograft rejection. We observed the expansion of regulatory T cells after co-culture with airway epithelial cells. The third aim will examine how signals associated with ischemia reperfusion injury regulate the ability of airway epithelial cells to expand regulatory T cells and whether regulatory T cells, expanded through co-culture with airway epithelial cells can prevent ischemia reperfusion injury-mediated lung allograft rejection. PUBLIC HEALTH RELEVANCE: Lung transplantation has become an established therapy for patients suffering from end stage lung disease. The survival after lung transplantation remains considerably worse as compared to other organs such as the heart and the liver. A major obstacle to the success of lung transplantation is ischemia reperfusion injury. We propose to study how ischemia reperfusion injury impacts lung graft survival utilizing a novel mouse model.